(US4996382-A)      Prepn. of hydrocarbons with at least 2C, comprises contacting a methane-contg. gas at 500-1500 deg.C with an 02 -contg. gas in the presence of a catalyst to effect oxidative coupling. The catalyst comprises a single - crystal, high purity and ultra-fine powdery Mg oxide obtd. by a gas-phase oxidn. method, and an alkali metal oxide, pref. in an amt. of 1-20 (1-10) mol.%    ADVANTAGE -   Conversion of methane is high and C2-selectivity is high. The catalyst has a long life and is cheap. (9pp)    (US4997802-A)      A catalyst consists of A) a single crystal. high purity, ultrafinely divided MgO obtd. by gas phase oxidation and B) an alkali metal oxide. Hydrocarbons contg at least 2 C are obtd by contacting a CH2 contg gas with an O2 contg gas in presence of the catalyst to effect oxidative coupling.    The MgO has a particle size 0.01-0.2 micrometre and a purity at least 99.98%. The oxide contains 1-20, esp. 1-10 mol.% alkali element, esp Li, K, Rb or Na.B) also contains an oxide of an element 21 (Sc) to 30 (Zn) or 57 (La) to 71 (Lu).    ADVANTAGE -   C2H4 can be effectively produced from readily available starting materials contg. mainly CH4 by a dry method. (9pp)e    (DE3875327-G)      Hydrocarbons having at least 2 carbon atoms are prepd. by bringing a methane-contg. gas (I) maintained at 500-1500 deg.C into contact with an oxygen-containing gas (II) in presence of a novel catalyst comprising (a) single crystal, high purity, ultra-fine powdery magnesium oxide obtained by a gas phase oxidation method, (b) an alkali metal oxide, and opt. (c) at least one oxide of a metal of atomic number 21 (Sc) to 30 (Zn) or 57 (La) to 71 (Lu), having positive divalency or trivalency.    Pref. (a) is formed by bringing magnesium vapour into contact with an oxygen-contaning gas in a turbulently diffused state, using e.g. a double tube burner (described). Particle size is 0.01-0.2 micro m and purity at least 99.98%. (b) is Li, Na, K or Rb oxide, 1-10 mole %, and (c) is e.g. Fe, Co, Ni, Cu, Zn, La, Ce or Sm oxide, 1-10 mole %. These components may be added as oxide or as starting material capable of forming the oxide, e.g. hydroxide, carbonate, nitrate, acetate, alkoxide or acetylacetonate, e.g. by kneading or impregnation.    ADVANTAGE -   Conversion of methane and selectivity to C2 hydrocarbons (ethylene and ethane) are high, reaction temp. and catalyst cost are low.    (JP94074215-B2)      Hydrocarbons having at least 2 carbon atoms are prepd. by bringing a methane-contg. gas (I) maintained at 500-1500 deg.C into contact with an oxygen-containing gas (II) in presence of a novel catalyst comprising (a) single crystal, high purity, ultra-fine powdery magnesium oxide obtained by a gas phase oxidation method, (b) an alkali metal oxide, and opt. (c) at least one oxide of a metal of atomic number 21 (Sc) to 30 (Zn) or 57 (La) to 71 (Lu), having positive divalency or trivalency.    Pref. (a) is formed by bringing magnesium vapour into contact with an oxygen-containing gas in a turbulently diffused state, using e.g. a double tube burner (described). Particle size is 0.01-0.2 micro m and purity at least 99.98%. (b) is Li, Na, K or Rb oxide, 1-10 mole %, and (c) is e.g. Fe, Co, Ni, Cu, Zn, La, Ce or Sm oxide, 1-10 mole %. These components may be added as oxide or as starting material capable of forming the oxide, e.g. hydroxide, carbonate, nitrate, acetate, alkoxide or acetylacetonate, e.g. by kneading or impregnation.    ADVANTAGE -   Conversion of methane and selectivity to C2 hydrocarbons (ethylene and ethane) are high, reaction temp. and catalyst cost are low.